This invention presents new and useful improvements in the armature of an electrical motor. More particularly, it is directed to the provision of a protective collar for the bars of the commutator of an automotive starter motor.
The armature is the rotating member of the starter; and the commutator is that part of the armature upon which brushes ride and serve to conduct current from a battery to the windings of the armature, whereby rotation of the armature is effected.
The starter is associated with an automotive engine in such manner that rotation of the armature is transmitted through a flywheel to rotate the piston crankshaft from a condition of rest to a speed at which the engine will commence to rotate on its own. When this occurs, associated mechanism in the starter automatically functions to stop further rotation of the armature.
The high speed at which the armature is caused to run and the accompanying high torque required to effect turning and starting of the engine develop high centrifugal forces and other negative forces that have a damaging effect upon the commutator. In this respect, the commutator includes a succession of parallel bars about its periphery. These are insulated from one another and from the armature shaft by insulating material in which they are embedded. The bars are of thin copper sheeting, and are subject to being further thinned by the rubbing action of the brushes. The strong negative forces imparted to the commutator every time the armature is actuated to start the engine tend to urge the free ends of the bars away from the commutator and out of the insulation. In due time the free ends peel or lift upwardly from the commutator and become damaged so as to require repair. This may mean removal and replacement of the damaged commutator or, because of the expense required for repairs, it may mean discarding the whole armature and replacing it with a new one.
Accordingly, the general object of this invention is to provide inexpensive means for application to the commutator which will resist the tendency of the free ends of the bars to peel and will, accordingly, restrain them in place.
A more specific object of the invention is to provide a collar which can be mounted to the commutator and seated over the free ends of the bars, whereby the free ends of the bars will be held firmly in place and restrained from lifting or peeling away.
A further object of the invention is to provide a collar which will not only serve to retain the bars in place, but will also serve as a lubricated thrust washer for the commutator relative to the end frame of the starter's housing.
The collar is molded of firm electrical insulating material, such as a suitable plastic, and it is adapted to be securely seated in a fixed position upon the commutator by a suitable adhesive so that it will rotate with the commutator as a unit and integral part thereof.
The foregoing objects, features and advantages of the invention, as well as others, will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawing wherein an embodiment of the invention is illustrated. It is, however, to be expressly understood that the drawing is for purposes of illustration and description, and it is not to be construed as defining the limits of the invention.